The present invention relates to a technology of making authentication by inputting a password.
In a case where authentication is required on the occasion of log-in to a computer and opening a file, it is a general practice that a user inputs a password from on a keyboard (including a virtual keyboard).
This password might be, however, presumed by others because of there being many users who set their easy-to-memorize birth days, telephone numbers, etc as the passwords.
Further, if the number of digits of the password is set excessively large, the user is unable to memorize the password, and the usability declines, so that the password is set with a small number of digits in many cases. The password having the small number of digits has, however, a possibility of receiving unauthorized accesses by a brute force attack.
Hence, there are proposed a variety of methods of strengthening the security by use of multiple additional/substitutive means such as a smartcard, fingerprints and a TPM (Trusted Platform Module).
Moreover, technologies disclosed in, e.g., the following Patent documents 1, 2 are given as the prior arts related to the invention of the present application.                [Patent document 1] Japanese Patent Application Laid-Open Publication No.2000-339084        [Patent document 2] Japanese Patent Application Laid-Open Publication No.2005-50251        